I think if you are trying to do spleef you could accomplish this with the following system:

1) Build the spleef arena out of obsidian mainly, with the floor being of dirt. Build it high above a ground pit (also of obsidian). You can maybe put lava on top of obsidian for a dramatic effect. (I doubt people would bring buckets.) I would put a clear rule at the entrance that only shovels (or even a certain type of shovel to prevent efficiency) are permitted into the pit.

2) Players pay their entry fees and gain access to the spleef arena. You can have a button and grant use flags to players as they pay, so they can go through a doorway and drop down into the ring. If someone else decides to sneak in to the arena without paying, you take away their move flag.

3) Once players are in, you use a keyboard macro to do a countdown and grant build rights at the same instant to all players. As each of these are just keyboard output, you can use a tool like AutoHotkey to manage it and build a script where you enter the names of players, and it does something like:// Type 'Spleef Match Starting Shortly'// Grab names of each player through a prompt// Type 3// Wait 1 second// Type 2// Wait 1 second// Type 1// Wait 1 second// Grant build flag to all players by typing the command for each// Type Go

4) If anyone decides to abuse the system and starts destroying the obsidian, you can take away their move and build flag. I would build a macro to do that too so it can happen very quickly before they can do much damage. Keep in mind someone in the pit could teleport back into your main res area and start destroying stuff so that's why you need a macro to get them really fast because if they take your stuff, you probably wont get it back. (Most people would not do this, and of course they'd get banned, but you have to have a precaution to protect your stuff. Some people can get upset if they lose at games and take it out on you instead in an unhealthy way.)

5) At the end of the match, use a macro to reset the flags before announcing the winner. There is a flag reset command, but you likely have default flags that you want to have added back again (such as a trusted friend), so that's why a macro helps so you don't have to do it all manually.

Automating actions, including - but not limited to - using auto-clickers, is legal as long as you are not AFK while doing so. You must be aware, and able to respond to staff and Minecraft at all times.